Refactor Compilation error to contain a Token (#535)

Use a `Token` to represent the error context, instead of a mess of
fields. Remove write_message_context in favor of `Token::write_context`.

justfile

@@ -34,7 +34,7 @@ check:
 	cargo check
 
 watch +COMMAND='test':
-	cargo watch --clear --exec build --exec "{{COMMAND}}"
+	cargo watch --clear --exec "{{COMMAND}}"
 
 man:
 	cargo build --features help4help2man

src/assignment_resolver.rs

@@ -40,13 +40,17 @@ impl<'a: 'b, 'b> AssignmentResolver<'a, 'b> {
       self.evaluated.insert(name);
     } else {
       let message = format!("attempted to resolve unknown assignment `{}`", name);
-      return Err(CompilationError {
+      let token = Token {
         src: "",
         offset: 0,
         line: 0,
         column: 0,
-        width: 0,
+        length: 0,
+        kind: TokenKind::Unspecified,
+      };
+      return Err(CompilationError {
         kind: Internal { message },
+        token,
       });
     }
     Ok(())

src/common.rs

@@ -35,10 +35,7 @@ pub(crate) use unicode_width::UnicodeWidthChar;
 pub(crate) use crate::{config_error, keyword, search_error, setting};
 
 // functions
-pub(crate) use crate::{
+pub(crate) use crate::{default::default, empty::empty, load_dotenv::load_dotenv, output::output};
-  default::default, empty::empty, load_dotenv::load_dotenv, output::output,
-  write_message_context::write_message_context,
-};
 
 // traits
 pub(crate) use crate::{

src/compilation_error.rs

@@ -1,13 +1,9 @@
 use crate::common::*;
 
 #[derive(Debug, PartialEq)]
-pub(crate) struct CompilationError<'a> {
+pub(crate) struct CompilationError<'src> {
-  pub(crate) src: &'a str,
+  pub(crate) token: Token<'src>,
-  pub(crate) offset: usize,
+  pub(crate) kind: CompilationErrorKind<'src>,
-  pub(crate) line: usize,
-  pub(crate) column: usize,
-  pub(crate) width: usize,
-  pub(crate) kind: CompilationErrorKind<'a>,
 }
 
 impl Error for CompilationError<'_> {}
@@ -25,7 +21,7 @@ impl Display for CompilationError<'_> {
           f,
           "Alias `{}` defined on line {} shadows recipe `{}` defined on line {}",
           alias,
-          self.line.ordinal(),
+          self.token.line.ordinal(),
           alias,
           recipe_line.ordinal(),
         )?;
@@ -90,7 +86,7 @@ impl Display for CompilationError<'_> {
           "Alias `{}` first defined on line {} is redefined on line {}",
           alias,
           first.ordinal(),
-          self.line.ordinal(),
+          self.token.line.ordinal(),
         )?;
       }
       DuplicateDependency { recipe, dependency } => {
@@ -106,7 +102,7 @@ impl Display for CompilationError<'_> {
           "Recipe `{}` first defined on line {} is redefined on line {}",
           recipe,
           first.ordinal(),
-          self.line.ordinal()
+          self.token.line.ordinal()
         )?;
       }
       DuplicateSet { setting, first } => {
@@ -115,7 +111,7 @@ impl Display for CompilationError<'_> {
           "Setting `{}` first set on line {} is redefined on line {}",
           setting,
           first.ordinal(),
-          self.line.ordinal(),
+          self.token.line.ordinal(),
         )?;
       }
       DependencyHasParameters { recipe, dependency } => {
@@ -223,14 +219,6 @@ impl Display for CompilationError<'_> {
 
     write!(f, "{}", message.suffix())?;
 
-    write_message_context(
+    self.token.write_context(f, Color::fmt(f).error())
-      f,
-      Color::fmt(f).error(),
-      self.src,
-      self.offset,
-      self.line,
-      self.column,
-      self.width,
-    )
   }
 }

src/lexer.rs

@@ -11,15 +11,15 @@ use TokenKind::*;
 /// regex-based lexer, which was slower and generally godawful. However,
 /// this should not be taken as a slight against regular expressions,
 /// the lexer was just idiosyncratically bad.
-pub(crate) struct Lexer<'a> {
+pub(crate) struct Lexer<'src> {
   /// Source text
-  src: &'a str,
+  src: &'src str,
   /// Char iterator
-  chars: Chars<'a>,
+  chars: Chars<'src>,
   /// Tokens
-  tokens: Vec<Token<'a>>,
+  tokens: Vec<Token<'src>>,
   /// State stack
-  state: Vec<State<'a>>,
+  state: Vec<State<'src>>,
   /// Current token start
   token_start: Position,
   /// Current token end
@@ -28,14 +28,14 @@ pub(crate) struct Lexer<'a> {
   next: Option<char>,
 }
 
-impl<'a> Lexer<'a> {
+impl<'src> Lexer<'src> {
   /// Lex `text`
   pub(crate) fn lex(src: &str) -> CompilationResult<Vec<Token>> {
     Lexer::new(src).tokenize()
   }
 
   /// Create a new Lexer to lex `text`
-  fn new(src: &'a str) -> Lexer<'a> {
+  fn new(src: &'src str) -> Lexer<'src> {
     let mut chars = src.chars();
     let next = chars.next();
 
@@ -58,7 +58,7 @@ impl<'a> Lexer<'a> {
 
   /// Advance over the chracter in `self.next`, updating
   /// `self.token_end` accordingly.
-  fn advance(&mut self) -> CompilationResult<'a, ()> {
+  fn advance(&mut self) -> CompilationResult<'src, ()> {
     match self.next {
       Some(c) => {
         let len_utf8 = c.len_utf8();
@@ -84,7 +84,7 @@ impl<'a> Lexer<'a> {
   }
 
   /// Lexeme of in-progress token
-  fn lexeme(&self) -> &'a str {
+  fn lexeme(&self) -> &'src str {
     &self.src[self.token_start.offset..self.token_end.offset]
   }
 
@@ -104,7 +104,7 @@ impl<'a> Lexer<'a> {
   }
 
   /// Un-lexed text
-  fn rest(&self) -> &'a str {
+  fn rest(&self) -> &'src str {
     &self.src[self.token_end.offset..]
   }
 
@@ -124,7 +124,7 @@ impl<'a> Lexer<'a> {
   }
 
   /// Get current state
-  fn state(&self) -> CompilationResult<'a, State<'a>> {
+  fn state(&self) -> CompilationResult<'src, State<'src>> {
     if self.state.is_empty() {
       Err(self.internal_error("Lexer state stack empty"))
     } else {
@@ -133,7 +133,7 @@ impl<'a> Lexer<'a> {
   }
 
   /// Pop current state from stack
-  fn pop_state(&mut self) -> CompilationResult<'a, ()> {
+  fn pop_state(&mut self) -> CompilationResult<'src, ()> {
     if self.state.pop().is_none() {
       Err(self.internal_error("Lexer attempted to pop in start state"))
     } else {
@@ -158,26 +158,31 @@ impl<'a> Lexer<'a> {
   }
 
   /// Create an internal error with `message`
-  fn internal_error(&self, message: impl Into<String>) -> CompilationError<'a> {
+  fn internal_error(&self, message: impl Into<String>) -> CompilationError<'src> {
-    // Use `self.token_end` as the location of the error
+    let token = Token {
-    CompilationError {
       src: self.src,
       offset: self.token_end.offset,
       line: self.token_end.line,
       column: self.token_end.column,
-      width: 0,
+      length: 0,
+      kind: Unspecified,
+    };
+
+    // Use `self.token_end` as the location of the error
+    CompilationError {
       kind: CompilationErrorKind::Internal {
         message: message.into(),
       },
+      token,
     }
   }
 
   /// Create a compilation error with `kind`
-  fn error(&self, kind: CompilationErrorKind<'a>) -> CompilationError<'a> {
+  fn error(&self, kind: CompilationErrorKind<'src>) -> CompilationError<'src> {
     // Use the in-progress token span as the location of the error.
 
     // The width of the error site to highlight depends on the kind of error:
-    let width = match kind {
+    let length = match kind {
       // highlight ' or "
       UnterminatedString => 1,
       // highlight `
@@ -186,26 +191,24 @@ impl<'a> Lexer<'a> {
       _ => self.lexeme().len(),
     };
 
-    CompilationError {
+    let token = Token {
+      kind: Unspecified,
       src: self.src,
       offset: self.token_start.offset,
       line: self.token_start.line,
       column: self.token_start.column,
-      width,
+      length,
-      kind,
+    };
-    }
+
+    CompilationError { token, kind }
   }
 
   fn unterminated_interpolation_error(
     &self,
-    interpolation_start: Position,
+    interpolation_start: Token<'src>,
-  ) -> CompilationError<'a> {
+  ) -> CompilationError<'src> {
     CompilationError {
-      src: self.src,
+      token: interpolation_start,
-      offset: interpolation_start.offset,
-      line: interpolation_start.line,
-      column: interpolation_start.column,
-      width: 2,
       kind: UnterminatedInterpolation,
     }
   }
@@ -251,7 +254,7 @@ impl<'a> Lexer<'a> {
   }
 
   /// Consume the text and produce a series of tokens
-  fn tokenize(mut self) -> CompilationResult<'a, Vec<Token<'a>>> {
+  fn tokenize(mut self) -> CompilationResult<'src, Vec<Token<'src>>> {
     loop {
       if self.token_start.column == 0 {
         self.lex_line_start()?;
@@ -287,7 +290,7 @@ impl<'a> Lexer<'a> {
   }
 
   /// Handle blank lines and indentation
-  fn lex_line_start(&mut self) -> CompilationResult<'a, ()> {
+  fn lex_line_start(&mut self) -> CompilationResult<'src, ()> {
     let nonblank_index = self
       .rest()
       .char_indices()
@@ -384,7 +387,7 @@ impl<'a> Lexer<'a> {
   }
 
   /// Lex token beginning with `start` in normal state
-  fn lex_normal(&mut self, start: char) -> CompilationResult<'a, ()> {
+  fn lex_normal(&mut self, start: char) -> CompilationResult<'src, ()> {
     match start {
       '@' => self.lex_single(At),
       '[' => self.lex_single(BracketL),
@@ -418,9 +421,9 @@ impl<'a> Lexer<'a> {
   /// Lex token beginning with `start` in interpolation state
   fn lex_interpolation(
     &mut self,
-    interpolation_start: Position,
+    interpolation_start: Token<'src>,
     start: char,
-  ) -> CompilationResult<'a, ()> {
+  ) -> CompilationResult<'src, ()> {
     // Check for end of interpolation
     if self.rest_starts_with("}}") {
       // Pop interpolation state
@@ -437,7 +440,7 @@ impl<'a> Lexer<'a> {
   }
 
   /// Lex token beginning with `start` in text state
-  fn lex_text(&mut self) -> CompilationResult<'a, ()> {
+  fn lex_text(&mut self) -> CompilationResult<'src, ()> {
     enum Terminator {
       Newline,
       NewlineCarriageReturn,
@@ -482,30 +485,31 @@ impl<'a> Lexer<'a> {
         self.lex_double(Eol)
       }
       Interpolation => {
+        self.lex_double(InterpolationStart)?;
         self.state.push(State::Interpolation {
-          interpolation_start: self.token_start,
+          interpolation_start: self.tokens[self.tokens.len() - 1],
         });
-        self.lex_double(InterpolationStart)
+        Ok(())
       }
       EndOfFile => self.pop_state(),
     }
   }
 
   /// Lex token beginning with `start` in indented state
-  fn lex_indented(&mut self) -> CompilationResult<'a, ()> {
+  fn lex_indented(&mut self) -> CompilationResult<'src, ()> {
     self.state.push(State::Text);
     Ok(())
   }
 
   /// Lex a single character token
-  fn lex_single(&mut self, kind: TokenKind) -> CompilationResult<'a, ()> {
+  fn lex_single(&mut self, kind: TokenKind) -> CompilationResult<'src, ()> {
     self.advance()?;
     self.token(kind);
     Ok(())
   }
 
   /// Lex a double character token
-  fn lex_double(&mut self, kind: TokenKind) -> CompilationResult<'a, ()> {
+  fn lex_double(&mut self, kind: TokenKind) -> CompilationResult<'src, ()> {
     self.advance()?;
     self.advance()?;
     self.token(kind);
@@ -513,7 +517,7 @@ impl<'a> Lexer<'a> {
   }
 
   /// Lex a token starting with ':'
-  fn lex_colon(&mut self) -> CompilationResult<'a, ()> {
+  fn lex_colon(&mut self) -> CompilationResult<'src, ()> {
     self.advance()?;
 
     if self.next_is('=') {
@@ -527,7 +531,7 @@ impl<'a> Lexer<'a> {
   }
 
   /// Lex a token starting with '{'
-  fn lex_brace_l(&mut self) -> CompilationResult<'a, ()> {
+  fn lex_brace_l(&mut self) -> CompilationResult<'src, ()> {
     if !self.rest_starts_with("{{") {
       self.advance()?;
 
@@ -538,7 +542,7 @@ impl<'a> Lexer<'a> {
   }
 
   /// Lex a token starting with '}'
-  fn lex_brace_r(&mut self) -> CompilationResult<'a, ()> {
+  fn lex_brace_r(&mut self) -> CompilationResult<'src, ()> {
     if !self.rest_starts_with("}}") {
       self.advance()?;
 
@@ -549,7 +553,7 @@ impl<'a> Lexer<'a> {
   }
 
   /// Lex a carriage return and line feed
-  fn lex_cr_lf(&mut self) -> CompilationResult<'a, ()> {
+  fn lex_cr_lf(&mut self) -> CompilationResult<'src, ()> {
     if !self.rest_starts_with("\r\n") {
       // advance over \r
       self.advance()?;
@@ -561,7 +565,7 @@ impl<'a> Lexer<'a> {
   }
 
   /// Lex name: [a-zA-Z_][a-zA-Z0-9_]*
-  fn lex_identifier(&mut self) -> CompilationResult<'a, ()> {
+  fn lex_identifier(&mut self) -> CompilationResult<'src, ()> {
     // advance over initial character
     self.advance()?;
 
@@ -579,7 +583,7 @@ impl<'a> Lexer<'a> {
   }
 
   /// Lex comment: #[^\r\n]
-  fn lex_comment(&mut self) -> CompilationResult<'a, ()> {
+  fn lex_comment(&mut self) -> CompilationResult<'src, ()> {
     // advance over #
     self.advance()?;
 
@@ -593,7 +597,7 @@ impl<'a> Lexer<'a> {
   }
 
   /// Lex backtick: `[^\r\n]*`
-  fn lex_backtick(&mut self) -> CompilationResult<'a, ()> {
+  fn lex_backtick(&mut self) -> CompilationResult<'src, ()> {
     // advance over initial `
     self.advance()?;
 
@@ -612,7 +616,7 @@ impl<'a> Lexer<'a> {
   }
 
   /// Lex whitespace: [ \t]+
-  fn lex_whitespace(&mut self) -> CompilationResult<'a, ()> {
+  fn lex_whitespace(&mut self) -> CompilationResult<'src, ()> {
     while self.next_is_whitespace() {
       self.advance()?
     }
@@ -623,7 +627,7 @@ impl<'a> Lexer<'a> {
   }
 
   /// Lex raw string: '[^']*'
-  fn lex_raw_string(&mut self) -> CompilationResult<'a, ()> {
+  fn lex_raw_string(&mut self) -> CompilationResult<'src, ()> {
     // advance over opening '
     self.advance()?;
 
@@ -646,7 +650,7 @@ impl<'a> Lexer<'a> {
   }
 
   /// Lex cooked string: "[^"\n\r]*" (also processes escape sequences)
-  fn lex_cooked_string(&mut self) -> CompilationResult<'a, ()> {
+  fn lex_cooked_string(&mut self) -> CompilationResult<'src, ()> {
     // advance over opening "
     self.advance()?;
 
@@ -780,7 +784,7 @@ mod tests {
       Dedent | Eof => "",
 
       // Variable lexemes
-      Text | StringCooked | StringRaw | Identifier | Comment | Backtick => {
+      Text | StringCooked | StringRaw | Identifier | Comment | Backtick | Unspecified => {
         panic!("Token {:?} has no default lexeme", kind)
       }
     }
@@ -808,22 +812,24 @@ mod tests {
     offset: usize,
     line: usize,
     column: usize,
-    width: usize,
+    length: usize,
     kind: CompilationErrorKind,
   ) {
-    let expected = CompilationError {
-      src,
-      offset,
-      line,
-      column,
-      width,
-      kind,
-    };
-
     match Lexer::lex(src) {
-      Ok(_) => panic!("Lexing succeeded but expected: {}\n{}", expected, src),
+      Ok(_) => panic!("Lexing succeeded but expected"),
-      Err(actual) => {
+      Err(have) => {
-        assert_eq!(actual, expected);
+        let want = CompilationError {
+          token: Token {
+            kind: have.token.kind,
+            src,
+            offset,
+            line,
+            column,
+            length,
+          },
+          kind,
+        };
+        assert_eq!(have, want);
       }
     }
   }

src/lib.rs

@@ -87,7 +87,6 @@ mod use_color;
 mod variables;
 mod verbosity;
 mod warning;
-mod write_message_context;
 
 pub use crate::run::run;
 

src/parser.rs

@@ -702,24 +702,26 @@ mod tests {
     offset: usize,
     line: usize,
     column: usize,
-    width: usize,
+    length: usize,
     kind: CompilationErrorKind,
   ) {
-    let expected = CompilationError {
-      src,
-      offset,
-      line,
-      column,
-      width,
-      kind,
-    };
-
     let tokens = Lexer::lex(src).expect("Lexing failed in parse test...");
 
     match Parser::parse(&tokens) {
-      Ok(_) => panic!("Parsing succeeded but expected: {}\n{}", expected, src),
+      Ok(_) => panic!("Parsing unexpectedly succeeded"),
-      Err(actual) => {
+      Err(have) => {
-        assert_eq!(actual, expected);
+        let want = CompilationError {
+          token: Token {
+            kind: have.token.kind,
+            src,
+            offset,
+            line,
+            column,
+            length,
+          },
+          kind,
+        };
+        assert_eq!(have, want);
       }
     }
   }

src/runtime_error.rs

@@ -82,6 +82,17 @@ impl Error for RuntimeError<'_> {
   }
 }
 
+impl<'a> RuntimeError<'a> {
+  fn context(&self) -> Option<Token> {
+    use RuntimeError::*;
+    match self {
+      FunctionCall { function, .. } => Some(function.token()),
+      Backtick { token, .. } => Some(*token),
+      _ => None,
+    }
+  }
+}
+
 impl<'a> Display for RuntimeError<'a> {
   fn fmt(&self, f: &mut Formatter) -> Result<(), fmt::Error> {
     use RuntimeError::*;
@@ -94,12 +105,10 @@ impl<'a> Display for RuntimeError<'a> {
     let message = color.message();
     write!(f, "{}", message.prefix())?;
 
-    let mut error_token: Option<Token> = None;
+    match self {
-
-    match *self {
       UnknownRecipes {
-        ref recipes,
+        recipes,
-        ref suggestion,
+        suggestion,
       } => {
         write!(
           f,
@@ -111,7 +120,7 @@ impl<'a> Display for RuntimeError<'a> {
           write!(f, "\nDid you mean `{}`?", suggestion)?;
         }
       }
-      UnknownOverrides { ref overrides } => {
+      UnknownOverrides { overrides } => {
         write!(
           f,
           "{} {} overridden on the command line but not present in justfile",
@@ -121,7 +130,7 @@ impl<'a> Display for RuntimeError<'a> {
       }
       ArgumentCountMismatch {
         recipe,
-        ref parameters,
+        parameters,
         found,
         min,
         max,
@@ -133,7 +142,7 @@ impl<'a> Display for RuntimeError<'a> {
             "Recipe `{}` got {} {} but {}takes {}",
             recipe,
             found,
-            Count("argument", found),
+            Count("argument", *found),
             if expected < found { "only " } else { "" },
             expected
           )?;
@@ -143,7 +152,7 @@ impl<'a> Display for RuntimeError<'a> {
             "Recipe `{}` got {} {} but takes at least {}",
             recipe,
             found,
-            Count("argument", found),
+            Count("argument", *found),
             min
           )?;
         } else if found > max {
@@ -152,7 +161,7 @@ impl<'a> Display for RuntimeError<'a> {
             "Recipe `{}` got {} {} but takes at most {}",
             recipe,
             found,
-            Count("argument", found),
+            Count("argument", *found),
             max
           )?;
         }
@@ -182,8 +191,8 @@ impl<'a> Display for RuntimeError<'a> {
       }
       Cygpath {
         recipe,
-        ref output_error,
+        output_error,
-      } => match *output_error {
+      } => match output_error {
         OutputError::Code(code) => {
           write!(
             f,
@@ -208,7 +217,7 @@ impl<'a> Display for RuntimeError<'a> {
             recipe
           )?;
         }
-        OutputError::Io(ref io_error) => {
+        OutputError::Io(io_error) => {
           match io_error.kind() {
             io::ErrorKind::NotFound => write!(
               f,
@@ -225,7 +234,7 @@ impl<'a> Display for RuntimeError<'a> {
             _ => write!(f, "Could not run `cygpath` executable:\n{}", io_error),
           }?;
         }
-        OutputError::Utf8(ref utf8_error) => {
+        OutputError::Utf8(utf8_error) => {
           write!(
             f,
             "Cygpath successfully translated recipe `{}` shebang interpreter path, \
@@ -234,28 +243,24 @@ impl<'a> Display for RuntimeError<'a> {
           )?;
         }
       },
-      Dotenv { ref dotenv_error } => {
+      Dotenv { dotenv_error } => {
         writeln!(f, "Failed to load .env: {}", dotenv_error)?;
       }
-      FunctionCall {
+      FunctionCall { function, message } => {
-        ref function,
-        ref message,
-      } => {
         writeln!(
           f,
           "Call to function `{}` failed: {}",
           function.lexeme(),
           message
         )?;
-        error_token = Some(function.token());
       }
       Shebang {
         recipe,
-        ref command,
+        command,
-        ref argument,
+        argument,
-        ref io_error,
+        io_error,
       } => {
-        if let Some(ref argument) = *argument {
+        if let Some(argument) = argument {
           write!(
             f,
             "Recipe `{}` with shebang `#!{} {}` execution error: {}",
@@ -295,12 +300,10 @@ impl<'a> Display for RuntimeError<'a> {
             recipe, n
           )?;
         } else {
+          write!(f, "Recipe `{}` failed for an unknown reason", recipe)?;
         }
       }
-      IoError {
+      IoError { recipe, io_error } => {
-        recipe,
-        ref io_error,
-      } => {
         match io_error.kind() {
           io::ErrorKind::NotFound => writeln!(
             f,
@@ -320,32 +323,23 @@ impl<'a> Display for RuntimeError<'a> {
           ),
         }?;
       }
-      TmpdirIoError {
+      TmpdirIoError { recipe, io_error } => writeln!(
-        recipe,
-        ref io_error,
-      } => writeln!(
         f,
         "Recipe `{}` could not be run because of an IO error while trying \
          to create a temporary directory or write a file to that directory`:{}",
         recipe, io_error
       )?,
-      Backtick {
+      Backtick { output_error, .. } => match output_error {
-        ref token,
-        ref output_error,
-      } => match *output_error {
         OutputError::Code(code) => {
           writeln!(f, "Backtick failed with exit code {}", code)?;
-          error_token = Some(*token);
         }
         OutputError::Signal(signal) => {
           writeln!(f, "Backtick was terminated by signal {}", signal)?;
-          error_token = Some(*token);
         }
         OutputError::Unknown => {
           writeln!(f, "Backtick failed for an unknown reason")?;
-          error_token = Some(*token);
         }
-        OutputError::Io(ref io_error) => {
+        OutputError::Io(io_error) => {
           match io_error.kind() {
             io::ErrorKind::NotFound => write!(
               f,
@@ -364,15 +358,13 @@ impl<'a> Display for RuntimeError<'a> {
               io_error
             ),
           }?;
-          error_token = Some(*token);
         }
-        OutputError::Utf8(ref utf8_error) => {
+        OutputError::Utf8(utf8_error) => {
           writeln!(
             f,
             "Backtick succeeded but stdout was not utf8: {}",
             utf8_error
           )?;
-          error_token = Some(*token);
         }
       },
       NoRecipes => {
@@ -387,10 +379,10 @@ impl<'a> Display for RuntimeError<'a> {
           "Recipe `{}` cannot be used as default recipe since it requires at least {} {}.",
           recipe,
           min_arguments,
-          Count("argument", min_arguments),
+          Count("argument", *min_arguments),
         )?;
       }
-      Internal { ref message } => {
+      Internal { message } => {
         write!(
           f,
           "Internal runtime error, this may indicate a bug in just: {} \
@@ -402,16 +394,8 @@ impl<'a> Display for RuntimeError<'a> {
 
     write!(f, "{}", message.suffix())?;
 
-    if let Some(token) = error_token {
+    if let Some(token) = self.context() {
-      write_message_context(
+      token.write_context(f, Color::fmt(f).error())?;
-        f,
-        Color::fmt(f).error(),
-        token.src,
-        token.offset,
-        token.line,
-        token.column,
-        token.lexeme().len(),
-      )?;
     }
 
     Ok(())

src/state.rs

@@ -1,9 +1,9 @@
 use crate::common::*;
 
 #[derive(Copy, Clone, PartialEq, Debug)]
-pub(crate) enum State<'a> {
+pub(crate) enum State<'src> {
   Normal,
-  Indented { indentation: &'a str },
+  Indented { indentation: &'src str },
   Text,
-  Interpolation { interpolation_start: Position },
+  Interpolation { interpolation_start: Token<'src> },
 }

src/testing.rs

@@ -42,26 +42,28 @@ pub(crate) fn analysis_error(
   offset: usize,
   line: usize,
   column: usize,
-  width: usize,
+  length: usize,
   kind: CompilationErrorKind,
 ) {
-  let expected = CompilationError {
-    src,
-    offset,
-    line,
-    column,
-    width,
-    kind,
-  };
-
   let tokens = Lexer::lex(src).expect("Lexing failed in parse test...");
 
   let module = Parser::parse(&tokens).expect("Parsing failed in analysis test...");
 
   match Analyzer::analyze(module) {
-    Ok(_) => panic!("Analysis succeeded but expected: {}\n{}", expected, src),
+    Ok(_) => panic!("Analysis unexpectedly succeeded"),
-    Err(actual) => {
+    Err(have) => {
-      assert_eq!(actual, expected);
+      let want = CompilationError {
+        token: Token {
+          kind: have.token.kind,
+          src,
+          offset,
+          line,
+          column,
+          length,
+        },
+        kind,
+      };
+      assert_eq!(have, want);
     }
   }
 }

src/token.rs

@@ -16,13 +16,64 @@ impl<'a> Token<'a> {
   }
 
   pub(crate) fn error(&self, kind: CompilationErrorKind<'a>) -> CompilationError<'a> {
-    CompilationError {
+    CompilationError { token: *self, kind }
-      column: self.column,
+  }
-      offset: self.offset,
+
-      line: self.line,
+  pub(crate) fn write_context(&self, f: &mut Formatter, color: Color) -> fmt::Result {
-      src: self.src,
+    let width = if self.length == 0 { 1 } else { self.length };
-      width: self.length,
+
-      kind,
+    let line_number = self.line.ordinal();
+    match self.src.lines().nth(self.line) {
+      Some(line) => {
+        let mut i = 0;
+        let mut space_column = 0;
+        let mut space_line = String::new();
+        let mut space_width = 0;
+        for c in line.chars() {
+          if c == '\t' {
+            space_line.push_str("    ");
+            if i < self.column {
+              space_column += 4;
+            }
+            if i >= self.column && i < self.column + width {
+              space_width += 4;
+            }
+          } else {
+            if i < self.column {
+              space_column += UnicodeWidthChar::width(c).unwrap_or(0);
+            }
+            if i >= self.column && i < self.column + width {
+              space_width += UnicodeWidthChar::width(c).unwrap_or(0);
+            }
+            space_line.push(c);
+          }
+          i += c.len_utf8();
+        }
+        let line_number_width = line_number.to_string().len();
+        writeln!(f, "{0:1$} |", "", line_number_width)?;
+        writeln!(f, "{} | {}", line_number, space_line)?;
+        write!(f, "{0:1$} |", "", line_number_width)?;
+        write!(
+          f,
+          " {0:1$}{2}{3:^<4$}{5}",
+          "",
+          space_column,
+          color.prefix(),
+          "",
+          space_width,
+          color.suffix()
+        )?;
+      }
+      None => {
+        if self.offset != self.src.len() {
+          write!(
+            f,
+            "internal error: Error has invalid line number: {}",
+            line_number
+          )?
+        }
+      }
     }
+    Ok(())
   }
 }

src/token_kind.rs

@@ -24,6 +24,7 @@ pub(crate) enum TokenKind {
   StringCooked,
   StringRaw,
   Text,
+  Unspecified,
   Whitespace,
 }
 
@@ -57,6 +58,7 @@ impl Display for TokenKind {
         StringRaw => "raw string",
         Text => "command text",
         Whitespace => "whitespace",
+        Unspecified => "unspecified",
       }
     )
   }

src/warning.rs

@@ -39,15 +39,7 @@ impl Display for Warning<'_> {
 
     if let Some(token) = self.context() {
       writeln!(f)?;
-      write_message_context(
+      token.write_context(f, Color::fmt(f).warning())?;
-        f,
-        Color::fmt(f).warning(),
-        token.src,
-        token.offset,
-        token.line,
-        token.column,
-        token.lexeme().len(),
-      )?;
     }
 
     Ok(())

src/write_message_context.rs

@@ -1,67 +0,0 @@
-use crate::common::*;
-
-pub(crate) fn write_message_context(
-  f: &mut Formatter,
-  color: Color,
-  text: &str,
-  offset: usize,
-  line: usize,
-  column: usize,
-  width: usize,
-) -> Result<(), fmt::Error> {
-  let width = if width == 0 { 1 } else { width };
-
-  let line_number = line.ordinal();
-  match text.lines().nth(line) {
-    Some(line) => {
-      let mut i = 0;
-      let mut space_column = 0;
-      let mut space_line = String::new();
-      let mut space_width = 0;
-      for c in line.chars() {
-        if c == '\t' {
-          space_line.push_str("    ");
-          if i < column {
-            space_column += 4;
-          }
-          if i >= column && i < column + width {
-            space_width += 4;
-          }
-        } else {
-          if i < column {
-            space_column += UnicodeWidthChar::width(c).unwrap_or(0);
-          }
-          if i >= column && i < column + width {
-            space_width += UnicodeWidthChar::width(c).unwrap_or(0);
-          }
-          space_line.push(c);
-        }
-        i += c.len_utf8();
-      }
-      let line_number_width = line_number.to_string().len();
-      writeln!(f, "{0:1$} |", "", line_number_width)?;
-      writeln!(f, "{} | {}", line_number, space_line)?;
-      write!(f, "{0:1$} |", "", line_number_width)?;
-      write!(
-        f,
-        " {0:1$}{2}{3:^<4$}{5}",
-        "",
-        space_column,
-        color.prefix(),
-        "",
-        space_width,
-        color.suffix()
-      )?;
-    }
-    None => {
-      if offset != text.len() {
-        write!(
-          f,
-          "internal error: Error has invalid line number: {}",
-          line_number
-        )?
-      }
-    }
-  }
-  Ok(())
-}